At present, Digital Subscriber Line Access Multiplexer (DSLAM) broadband access devices principally include an Asynchronous Transfer Mode DSLAM (ATM DSLAM) which is a broadband access device based on ATM switch and an Internet Protocol DSLAM (IP DSLAM) which is a broadband access device based on Virtual Local Area Network (VLAN)+Medium Access Control (MAC) switch.
Existing broadband access devices may, according to the device's form, be divided into two kinds: frame type and box type. As shown in FIG. 1, both kinds of the broadband access devices include four components: a subscriber interface functional module, a main control functional module, a switching functional module and a backplane connection functional module. Where, the subscriber interface functional module is used for providing access interfaces for subscribers, and different subscriber interface functional modules provide different access modes, including any or any combination of an Asymmetric Digital Subscriber Line (ADSL), a Very High Data Rate Digital Subscriber Line (VDSL), an Ethernet and a Symmetric High Data Rate Digital Subscriber Line (G.SHDSL), etc. In general, a broadband access device may provide a plurality of subscriber interface functional modules and each subscriber interface functional module may provide a plurality of line interfaces for the user to access. The main control functional module is used for providing the broadband access device with a system control and management function; the switching functional module is used for providing the whole broadband access device with service converging and processing function as well as a network side interface, and the backplane connection functional module is used for providing a connection and communication function between aforesaid functional modules.
The DSLAM broadband access device has seen development through such phases as those of a narrow band Time Division Multiplexing (TDM) switching kernel, an ATM switching kernel, an Ethernet switching/IP switching kernel, etc.
Another existing broadband access device is based on the Ethernet/IP switching kernel, which may, by using a network architecture of Ethernet Layer 2 (L2)/Layer 3 (L3) based switching, provide a higher switching capacity up to 10 Gbps-48 Gbps or even higher and an interface bandwidth based on a Fast Ethernet (FE)/Gigabit Ethernet (GE), even 10 GE, such that a bandwidth bottleneck is conquered. An Ethernet message bearer is used between the subscriber interface functional module and the main control switching functional module of the access device, a FE or a GE connection is used between the subscriber interface functional module and the main control functional module, and the switching sub-functional module is also based on the Ethernet switching.
As shown in FIG. 3, a service processing of the broadband access device based on the Ethernet/IP switching kernel is as follows: an ATM Virtual Channel (VC) bearer or an Ethernet message mode is used by the subscriber interface functional module to get service accessed, then an ATM cell is regrouped and converted back to an Ethernet message with a 802.1Q based VLAN ID added, and is transferred to the switching functional module via the Ethernet based FE/GE star bus on the backplane connection functional module, then the switching functional module forwards the service to corresponding output port through the VLAN+MAC address based learning and switching mode or through the L3 IP address based mode.